It has been observed that phase-contrast computed tomography (CT) imagery and CT Compton cross-section absorption imagery (obtained from a spectral material decomposition) are inflicted by relatively high image noise levels in the high frequency range for phase-contrast imaging and the low frequency range for spectral imaging, respectively. What is more, spectral material decomposition may require special detector hardware, in particular photon-counting and/or energy resolving detectors, which may be expensive to procure.